Coated articles are known in the art for use in window applications such as insulating glass (IG) window units, vehicle windows, monolithic windows, and/or the like. In certain example instances, designers of coated articles often strive for a combination of high visible transmission, substantially neutral color, low emissivity (or emittance), low sheet resistance (Rs), and/or low specific resistivity. High visible transmission and substantially neutral color may permit coated articles to be used in applications where these characteristics are desired such as in architectural or vehicle window applications, whereas low-emissivity (low-E), low sheet resistance, and low specific resistivity characteristics permit such coated articles to block significant amounts of IR radiation so as to reduce for example undesirable heating of vehicle or building interiors.
However, conventional coated articles are often lacking with respect to one or more of: (i) mechanical durability, and/or (ii) ability to realize a combination of good/high visible transmission (Tvis), high solar heat gain coefficient (SHGC), and low emissivity.
U.S. Pat. No. 6,210,784 in Example 2 discloses a layer stack of glass/TiO/ZnO/Ag/Ti/TiO/SnO/SiO/SiN. However, this coated article is silent as to SHGC and is only able to achieve a visible transmission of 78.6% measured monolithically.
In warm climates, low SHGC values are desired together with high visible transmission. Thus, the prior art typically desires low SHGC values which teaches away from example embodiments of this invention. However, in colder climates high SHGC values are often desired. SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculated from the full spectrum (Tvis, Rg and Rf) and may be measured with a spectrophotometer such as a Perkin Elmer 1050.
In view of the above, it will be appreciated that there exists a need in the art for a coated article including a coating (e.g., in the context of a monolithic or IG window unit) which has the ability to realize one or more of: (i) good durability, (ii) high SHGC, (iii) high Tvis, and/or (iv) low normal emissivity (En).
Certain example embodiments of this invention relate to a coated article having a low-emissivity (low-E) coating that includes at least one infrared (IR) reflecting layer of a material such as silver, gold, or the like, and a dielectric overcoat designed to increase solar heat gain coefficient (SHGC) and visible transmission (Tvis) of the coated article. A dielectric undercoat of the coating may also be designed to increase SHGC and/or visible transmission of the coated article in certain example embodiments. In certain example embodiments, the overcoat and/or undercoat are designed to increase SHGC and visible transmission while also providing for substantially neutral color and/or desirably low normal emittance (En). It has surprisingly been found that overcoat and/or undercoat designs herein advantageously provide for increased SHGC and/or visible transmission (Tvis) values of the coated article, without significantly reducing normal emissivity (En) and allowing for substantially neutral color.
In certain example embodiments, a double pane IG window unit including the coating (e.g., on surface #2 or surface #3) may have an SHGC value of at least 0.60, more preferably of at least 0.65; more preferably at least 0.66; and most preferably of at least 0.67. In certain example embodiments of this invention, coated articles are able to realize a visible transmission (TY or Tvis) of at least about 68%, more preferably at least about 70%, still more preferably of at least about 72%, more preferably of at least about 74%, more preferably of at least 80% measured monolithically, and most preferably of at least 85% measured monolithically; and a normal emissivity (En) of no greater than 0.2, more preferably no greater than 0.10, and most preferably no greater than 0.045. In certain example embodiments of this invention, coated articles can realize a combination of high visible transmission (Tvis) and a high solar heat gain coefficient (SHGC) which is desired for cold climates. In view of the above, it is possible to permit the coated article, such as an IG window unit for example, to realize excellent properties such as high SHGC, high visible transmission, low emissivity, and good durability. For coatings according to example embodiments of this invention, a high SHGC is preferred because the coating is adapted for use in northern climates. The high SHGC desired for this coating is the opposite of low SHGC values desired for coatings for use in southern/hot climates.
Coated articles herein may be used in the context of insulating glass (IG) window units, or in other suitable applications such as monolithic windows, laminated windows, and/or the like.
In an example embodiment of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer; an infrared (IR) reflecting layer comprising silver on the glass substrate, located over at least the first dielectric layer; a contact layer on the glass substrate located over and directly contacting the IR reflecting layer; a multilayer overcoat comprising a dielectric high index layer having a refractive index (n) of at least 2.2, a dielectric medium index layer having a refractive index (n) of from 1.9 to 2.1, and a dielectric low index layer having a refractive index of no greater than 1.7, and wherein the medium index layer is located between and directly contacting the high index layer and the low index layer; and wherein the coating has a normal emissivity (En) of no greater than 0.2, more preferably no greater than 0.10, still more preferably no greater than 0.045, and a visible transmission of at least 80% (more preferably at least 85%) measured monolithically.
In certain example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer; an infrared (IR) reflecting layer comprising silver on the glass substrate, located over at least the first dielectric layer; a contact layer on the glass substrate located over and directly contacting the IR reflecting layer; a multilayer overcoat comprising a dielectric high index layer having a refractive index (n) of at least 2.2, a dielectric medium index layer having a refractive index (n) of from 1.9 to 2.1, and a dielectric low index layer having a refractive index of no greater than 1.7, and wherein the medium index layer is located between and directly contacting the high index layer and the low index layer; a multilayer dielectric undercoat between the glass substrate and the IR reflecting layer, wherein the dielectric undercoat comprises the first dielectric layer which directly contacts the glass substrate and is a medium index layer having a refractive index (n) from 1.9 to 2.1, and a second dielectric layer which is a high index layer having a refractive index (n) of at least 2.2, and wherein in the undercoat the first dielectric layer is located between the glass substrate and the second dielectric layer; and wherein the coating has a normal emissivity (En) of no greater than 0.2.
In certain example embodiments of this invention, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer; an infrared (IR) reflecting layer comprising silver on the glass substrate, located over at least the first dielectric layer; a contact layer on the glass substrate located over and directly contacting the IR reflecting layer; a multilayer overcoat comprising a dielectric high index layer comprising an oxide of bismuth and/or titanium, and a dielectric low index layer having a refractive index of no greater than 1.7, and wherein the low index layer is located between at least the high index layer and the contact layer; and wherein the coating has a normal emissivity (En) of no greater than 0.2 and/or a visible transmission of at least 80% or at least 85% measured monolithically.